Gilbert -- who competes for charity -- has participated in dozens of duathlons and triathlons since he was 68.

To prepare for them, the pensioner has adopted a rigorous exercise routine which involves going to the gym, as well as bicycling for 25 miles weekly and swimming 50 laps every day, ThisIsSomerset.co.uk reports.

Gilbert, who has been crowned British duathlon champion in his age group seven times, credits a healthy lifestyle and charity work for his good health.

“The secret is staying stress-free, being happy, doing charity work and being positive. I don’t drink or smoke and I have regular check-ups," he said. “I also have a balanced diet with lots of fruit which helps ­tremendously -- I love nuts and bananas."

According to Burnham-On-Sea.com, Gilbert was given the title of the world’s oldest triathlete last year by the World Records Academy. The widower said he can't seem to stop himself from competing.

“I keep saying I’m going to give up soon but I always end up going back to do more. This triathlon was my third ‘last one.’ I just can’t give up,” he told the Mirror.

Gilbert, who in 2008 was awarded the distinguished MBE medal by Prince Charles for his charity work, admitted that his active lifestyle baffles some people, but he expressed hope that he might inspire others with his example.

"People think I’m bonkers but they inspire me to carry on and I inspire them to do something like this for charity," he said.